Over the past years, articles of carbon and graphite have found increasing use in commercial applications of many kinds the main development being in the increasing use of reinforced carbon and graphite articles which have improved physical properties and increased oxidation resistance at high temperatures. Bodies of this type are increasingly used in the aerospace and aviation fields, where resistance to corrosion, high temperature, thermal shock and excellent wear characteristics are required of the material to be used. In this connection articles consisting essentially of carbon or graphite fibers bound by a carbon or graphite matrix into a integral body have been found to be exceedingly useful. Reinforced carbon and graphite articles and the method of producing them is disclosed by Rohl and Robinson in U.S. Pat. No. 3,462,269, entitled "Process for Producing Reinforced Carbon and Graphite Bodies." Another method for producing laminated graphite articles is disclosed in U.S. Pat. No. 3,174,895 to Gibson et al.
A carbon or graphite article having improved oxidation resistance and increased strength is disclosed in U.S. Pat. No. 3,672,936 to Ehrenreich, the desired properties being achieved by the incorporation of the in situ reaction product of carbon and a boron containing additive. These carbon or graphite articles will retain high strength at temperatures on the order of 1000.degree. C. In addition, the coefficient of friction may be controlled by the choice of additive, so that a carbon or graphite article may be produced which has a coefficient of friction either substantially reduced, compared to that of a conventional carbon body, or else greater than that of a conventional body. This control of properties is, of course, highly desirable in the manufacture of carbon friction elements such as brake discs.
Carbon articles such as brake discs can be produced by forming carbon fibers into a suitable shape, pressure impregnating a carbonizable binder into the fiber shape, and firing the impregnated shape at sufficient temperature in an inert atmosphere to carbonize the binder, thereby causing the fibers to be bound into an integral body with a carbon binder. The impregnating and carbonizing steps can be repeated a number of times until the density of the article is at the desired level, normally 1.4 grams/cc. and higher. The carbon fiber shapes can be produced by building up layers of carbon cloth, a suitable additive being dispersed in the fiber shape in the form of finely divided particles between the fiber layers as the fibrous shape is being produced. To give the best reinforcing effect, the particle sizes of the additive are preferably on the order of 250 microns or smaller and the additive must be distributed uniformly over the surface of the carbon fiber. A satisfactory friction disc may comprise a considerable number of layers of carbon cloth, each layer of which should desirably have a uniform coating of the additive. The process for building up the discs has been rather tedious and difficult, due to the difficulty of distributing the additive in a uniform coating and to dusting and loss of additive due to the extremely fine particle size used. An apparatus of a semi-automatic type on which the discs could be assembled and the additive dispersed in a controlled manner is therefore desirable for the proper assembly and fabrication of carbon or graphite brake discs.